There has been an increasing trend in recent years towards incorporating many types of motion control devices in the same vehicle to control the motion of the vehicle. The effect produced by each of the different types of motion control devices may not always emerge in a manner independent of each other at the vehicle. There is a possibility of mutual interference. It is therefore important to sufficiently organize the interaction and coordination between respective motion control devices in developing a vehicle that incorporates a plurality of types of motion control devices.
For example, when it is required to incorporate a plurality of types of motion control devices in one vehicle in the development stage of a vehicle, it is possible to develop respective motion control devices independently of each other, and then implement the interaction and coordination between respective motion control devices in a supplemental or additional manner.
In the case of developing a plurality of types of motion control devices in the aforesaid manner, organization of the interaction and coordination between respective motion control devices requires much time and effort.
With regards to the scheme of incorporating a plurality of types of motion control devices in a vehicle, there is known the scheme of sharing the same actuator among the motion control devices. This scheme involves the problem of how the contention among the plurality of motion control devices, when required to operate the same actuator at the same time, is to be resolved.
In the above-described case where the interaction and coordination among a plurality of motion control devices are to be organized in a supplemental or additional manner after the motion control devices are developed independently of each other, it is difficult to solve the problem set forth above proficiently. In practice, the problem may be accommodated only by selecting an appropriate one of the plurality of motion control devices with precedence over the others, and dedicate the actuator to the selected motion control device alone.
An approach related to the problem set forth above in a vehicle incorporating a plurality of actuators to drive a vehicle in the desired behavior is disclosed in the following publications.
Japanese Patent Laying-Open No. 5-85228 (Document 1) discloses an electronic control system of a vehicle that can reduce the time required for development, and that can improve the reliability, usability, and maintenance feasibility of the vehicle. This electronic control system for a vehicle includes elements coacting for carrying out control tasks with reference to engine power, drive power and braking operation, and elements for coordinating the coaction of the elements to effect a control of operating performance of the motor vehicle in correspondence to a request of the driver. Respective elements are arranged in the form of a plurality of hierarchical levels. At least one of the coordinating elements of the hierarchical level is adapted for acting on the element of the next hierarchical level when translating the request of the driver into a corresponding operating performance of the motor vehicle thereby acting on a pre-given subordinate system of the driver-vehicle system while providing the performance required from the hierarchical level for this subordinate system.
By organizing the entire system in a hierarchy configuration in accordance with this electronic control system for a vehicle, an instruction can be conveyed only in the direction from an upper level to a lower level. The instruction to execute the driver's request is transmitted in this direction. Accordingly, a comprehensible structure of elements independent of each other is achieved. The linkage of individual systems can be reduced to a considerable level. The independency of respective elements allows the individual elements to be developed concurrently at the same time. Therefore, each element can be developed in accordance with a predetermined object. Only a few interfaces with respect to the higher hierarchical level and a small number of interfaces for the lower hierarchical level have to be taken into account. Accordingly, optimization of the totality of the driver and the vehicle electronic control system with respect to energy consumption, environmental compatibility, safety and comfort can be achieved. As a result, a vehicle electronic control system can be provided, allowing reduction in the development time, and improvement in reliability, usability, and maintenance feasibility of a vehicle.
Japanese Patent Laying-Open No. 2003-191774 (Document 2) discloses a integrated type vehicle motion control device adapting in a hierarchy manner a software configuration for a device that controls a plurality of actuators in an integrated manner to execute motion control of a plurality of different types in a vehicle, whereby the hierarchy structure is optimized from the standpoint of practical usage. This integrated vehicle motion control device controls a plurality of actuators in an integrated manner through a computer based on information related to driving a vehicle by a driver to execute a plurality of types of vehicle motion control for the vehicle. At least the software configuration among the hardware configuration and software configuration includes a plurality of elements organized in hierarchy in a direction from the driver towards the plurality of actuators. The plurality of elements include: (a) a control unit determining the target vehicle state quantity based on the driving-related information at the higher level; and (b) an execution unit receiving the determined target vehicle state quantity as an instruction from the control unit to execute the received instruction via at least one of the plurality of actuators at the lower level. The control unit includes an upper level control unit and a lower level control unit, each issuing an instruction to control the plurality of actuators in an integrated manner. The upper level control unit determines a first target vehicle state quantity based on the driving-related information without taking into account the dynamic behavior of the vehicle, and supplies the determined first target vehicle state quantity to the lower level control unit. The lower level control unit determines the second target vehicle state quantity based on the first target vehicle state quantity received from the upper level control unit, taking into account the dynamic behavior of the vehicle, and supplies the determined second target vehicle state quantity to the execution unit. Each of the upper level control unit, the lower level control unit, and the execution unit causes the computer to execute a plurality of modules independent of each other on the software configuration to realize unique functions thereof.
In accordance with this integrated type vehicle motion control device, at least the software configuration among the hardware configuration and software configuration is organized in a hierarchy structure so as to include: (a) a control unit determining a target vehicle state quantity based on driving-related information at the higher level in the direction from the driver to the plurality of actuators; and (b) an execution unit receiving the determined target vehicle state quantity as an instruction from the control unit to execute the received instruction via at least one of the plurality of actuators at the lower level. In other words, at least the software configuration is organized in hierarchal levels such that the control unit and the execution unit are separated from each other in this vehicle motion control device. Since the control unit and the execution unit are independent of each other from the software configuration perspective, respective stages of development, designing, design modification, debugging and the like can be effected without influencing the other. Respective stages can be carried out concurrently with each other. As a result, the period of the working stage required for the entire software configuration can be readily shortened by the integrated vehicle motion control device.
The electronic control system for a vehicle disclosed in Document 1 is disadvantageous in that the entire controllability of the vehicle is degraded when in the event of system failure at the upper hierarchical level since the entire system employs a hierarchy structure.
The integrated type vehicle motion control device disclosed in Document 2 specifically discloses the hierarchy structure of Document 1, and is directed to optimization of the hierarchy structure from the standpoint of practical usage. Specifically, the software configuration is divided into at least a control unit and an execution unit, independent of each other in the hierarchy level. Although this integrated type vehicle motion control device is advantageous from the standpoint of concurrent processing of development by virtue of independency thereof, the issue of depending upon the basic concept of hierarchy is not yet resolved.